Means for closing and opening multiplaten presses



July 7,1970 N. E. E. BOOK 3,518,724

MEANS FOR CLOSING AND OPENING MULTIPLATEN PRESSES Filed March 15, 1968 2 Sheets-Sheet 1 July 7, 1970 5, 500K 3,518,724

MEANS FOR CLOSING AND OPENING MULTIPLATEN PRESSES Filed March 15, 1968 2 Sheets-Sheet 2 United States Patent 3,518,724 MEANS FOR CLOSING AND OPENING MULTIPLATEN PRESSES Nils Evert Erling Book, Motala, Sweden, assignor to Aktiebolaget Motala Verkstad, Motala, Sweden, a corporation of Sweden Filed Mar. 15, 1968, Ser. No. 713,352

Claims priority, application Sweden, Mar. 28, 1967,

4,240/ 67 Int. Cl. B30b 7/02 U.S. Cl. 1816 3 Claims ABSTRACT OF THE DISCLOSURE Apparatus for closing and opening a multistory press having some of the press platens connected to a stationary press table by a direct linkage and other press platens mounted between and connected to the first named platens by support means independent of the direct linkage.

Multiplaten presses of conventional construction are normally designed in such a manner that the press platens rest on support members arranged step-wise, in the correct position for the removal of the pressed goods and charging of new goods when the press is fully opened. When closing the press the press platens are lifted from the support members by the vertically movable lower press table one at a time and stacked thereon, and when the press is opened the platens are returned singly to the said support members. The relative speed between the two press platens located in each deck or story during the closing and opening of said story is thus the same as the speed at which the lower press table moves.

' However, this conventional type of press presents certain serious disadvantages when used for some specific types of pressing work. When pressing dry, fibrous material, e.g. by the manufacture of particle board, the material will be blown out from between the platens if the stories are closed too quickly. When pressing different types of slabs, e.g. hot pressing of particle-board and fibreboard where so-called gloss plates or surface plates are used to give the material the desired'surface finish, impurities in the form of dust and dirt are sucked in between the gloss plates and the press platens if the stories are opened too quickly; thus, the press must too often be shut down for cleaning. The speed at which the press table moves must in these instances therefore be restricted to a valve lower than would otherwise be applied, which causes loss of time and reduced production.

Because the stories are closed one at a time, i.e. in series, the contact time between the pressed material and the overlying press platen varies in the different stories, which when hot pressing can cause unsuitable variations in the quality of the pressed product, particularly in those instances when the closing speed of the press must be restricted so that there is an appreciable time difference between the closing of the different stories. Also, since the press platens are stacked one on top of the other the surface pressure decreases during the pressing operation from story to story upwards in the press by an amount corresponding to the weight of the intermediate press platen. For instance, when hot pressing soft fibreboard a surface pressure is used during a portion of the pressing period which is of the same magnitude as the said variation in surface pressure and this causes uneven quality and thickness or density of the pressed sheets.

It is known, for instance, from the U.S. patent specifications 1,939,014, 2,586,474, 2,884,032, 2,913,027, 2,966,- 183, 3,009,495 and 3,050,777, to reduce the closing and opening speed of the separate stories relative to the speed of the movable press table and thereby eliminate those of the aforementioned disadvantages in conventional multistory presses which are associated with the fact that the press openings are closed and opened in series during movement of the movable press table. This is achieved in that all the movable press platens, including the one secured to the movable press table, are caused to move simultaneously in a direction towards or away from the press platen secured to the stationary press table at speeds which are proportional to, or approximately proportional to, the distance of respective press platens from the stationary press platen when the press is fully open. The relative movement between the two press platens in each story thus takes place simultaneously and at the same or substantially the same speed in all stories. Consequently, the closing and opening speed of the separate stories is equal to or approximately equal to the speed of movement of the press table divided by the number of stories, and it is possible to move the movable press table at high speed without blowing the material to be pressed out from between the platens and sucking in large quantities of dust and dirt between press platens and gloss plates. Further, the material to be pressed is brought into contact with the overlying press platen simultaneously or approximately simultaneously in all stories.

Theoretically it is possible to produce exactly the same relative speeds between the press platens and to obtain contact between the goods being pressed and the respective overlying press platens at exactly the same moment in all the stories, but owing to the varying thicknesses of the individual press platens and gloss plates etc., and owing to variations in the quantity of goods being pressed in the various stories, and because of mechanical deficiences in the arrangements for moving the press platens, in actual practice, slight deviations are always obtained between the different stories with regard to their relative closing and opening speeds, as well as the time at which contact occurs. These dissimilarities and deviations, however, lack practical significance and on occasions small differences in the relative speed of the platens and moment of contact have for some reason or other been caused intentionally.

Different arrangements for providing the said simultaneous movement of the press platens are also known, e.g. from the aforementioned patent specifications. Means arranged between the stationary press table or press platen and the movable press platens to fulfill this function include pantographs, levers cooperating with lifting rods or systems comprising cables or chains actuated by the movement of the movable press table to give the individual press platens the desired movement. In the majority of cases arrangements are also envisaged which, when contact is reached in the story openings and the actual pressing operation begins, prevent the occurring high pressing force from acting upon the arrangements which provide for movement of the press platens and damaging the same. In certain instances the arrangements are also designed so that they partially or completely eliminate the effect of the weight of the press platens on the surface pressures in the different stories during the pressing operation.

However, hitherto arrangements of this nature have only been used to a very limited degree, at least when conconcerning multistory presses for hot pressing particle board, fibreboard and the like, owing to the fact that they are complicated and expensive. They are also space eonsuming and in the case of a press having twenty stories or more it is very difficult to provide sufficient space to enable said arrangements to be made sufficiently robust and reliable in operation. In general the possibiity afforded by the arrangements of reducing the pressing time by increasing the speed of movement of the press table has not been utilized to the full extent. For instance, an increase in the table speed of twenty times the normal speed of conventional presses, places such large requirements on the hydraulic equipment and increases the price of this press to such an extent that considerably lower speeds have been adopted.

The object of the present invention is to provide in multistory presses a sutficiently low relative speed between the press platens in the individual stories in relation to the speed of the movable press table in order to substantially reduce or completely eliminate the disadvantages manifest in conventional multistory presses without it being necessary to resort to complicated, expensive and technically difficult arrangements. This object is fulfilled by the arrangement according to the invention in that it has obtained the characterizing features disclosed in the claims.

The invention will now be described with reference to the accompanying drawings, where FIGS. 1 and 2 show a vertical cross section through the press tables and the press platens in a multistory press provided with an arrangement according to the invention, in an open and closed position of the press respectively, and

FIG. 3 shows in a cut-away vertical view a detail of an alternative embodiment of the arrangement according to the invention.

For the sake of clarity FIGS. 1 and 2 do not show the entire press but only the upper stationary press table 1 together with the press platen 2 secured thereto, the lower movable press table 4 together with the press platen 5 secured thereto, and the intermediate press platens 6, 7, 8. The press platens may be provided with means (not shown) for heating the same, in which case heat insulating inserts 3 are placed between the press tables 1, 4 and the press platens 2, 5 secured thereto. In FIG. 1 the press tables and press platens are shown in the position which they occupy when the press is fully open and in FIG. 2 the position which they occupywhen the press is fully closed during pressing of goods in the various stories.

Each story in the press is provided with a gloss plate 9, mounted below the upper press platen by means of when charging and removing the material. The material 13 to be pressed is shown in FIG. 1 placed on the wear plates in the fully open stories. In FIG. 2 the material fills the closed stories. The material is often placed on an extra so-calledconveyor plate when charged to the press, said conveyor plate remains in the press during the pressing operation and is removed together with the pressed goods; these conveyor plates however, have not been shown in the drawing. To bring about the desired movement of the press platens during the closing and opening of the press the press is provided with a number of lever mechanisms of known design,'suitably two such mechanisms on either long side of the press. Each mechanism comprises a lever 14, the one end of which is pivotally connected with the stationary press table 1 and the other end of which is pivotally connected with the upper end of an operating rod 15, the lower end of which rod is pivotally connected with the movable press table 4. Acting between the lever 14 and each third press platen 6 is a lifting rod 16 which is pivotally connected at its lower end with lugs secured to the press platens 6 and at the upper end with the lever 14, at such a distance from the pivot point of the lever at the stationary press table 1 that upon movement of the movable press table 4 together with the press platen 5 the press platens 6 move at speeds which relate to the speed of movement of the press table 4 approximately as the distance of respective press platens 6 from the press platen 2 on the stationary press platen 1 relates to the distance between the press platens 5 and 2 when the press is fully open. The lifting rods 16 may suitably be provided with means 17 which permit the length of said rods to change during the actual pressing operation, to compensate for variations in thickness of press platens and surface plates, for varying quantity of pressed goods in different stories of the press etc., and which eliminate the effect of the weight of the press platens on the surface pressure during the pressing operation, as described, for instance, in the US. Pat. No. 3,361,056.

The press platens 7 nearest and below the stationary press platen 2 and the movable press platens 6 suspended by the lifting rods 16 are suspended from said platens 2 and 6 by means of bolts 18 provided with nuts 19, said bolts being inserted through holes in shoulder members or abutments 20 secured to the press platens and preferably arranged at two positions on either long side of the press in the proximity of the four lever mechanisms. The press platens 8 located below the press platens 7 are also suspended from said press platens 7 by means of similar arrangements, displaced somewhat in the longitudinal direction of the press so that the two groups of suspending means are free from each other when the press is closed.

When closing the described press the press platens move in the following manner: When the press table 4 together with the press platen 5 begins to move towards the stationary press table 1 the whole of the lowermost group of press platens 6, 7, 8 begin simultaneously to move in the same direction at approximately two-thirds the speed at which the press table moves, and the group of press platens 6, 7, 8 lying above said first group move in the same direction at approximately one-third the speed of said press table, while the top group of press platens 2,7, 8- do not move at all. Thus, all press openings below the press platens 8 are closed at a relative speed between the press'platens which is approximately one-third the speed of movement of the press table 4 while the remaining press openings still remain fully open. When the press openings below the platens Shave been fully closed after the press table 4 has moved through approximately one-third ofthe total path' of movement, the greater speed of the underlying press platen is imparted to the press platens 8 and all' press openingsbetween the press platens 7 and '8 are-closed during the next one-third of the path of movement of the press table 4 at a relative speed between the'platens, which is also approximately one-third the speed of-the press table, while the press openings above the platens 7 are still fully open. When the press openings below the press platens 7 have been fully closed, i.e. after the press table 4 has completed the second third of its total travel, the greater speed of the underlying press platen is in turn imparted to the respective press platens platens 7, after which the press openings between the platens 7 and 8 are opened, and finally the openings below the platens 8.

By virtue of the devices 17 in the lifting rods 16 it is possible to counteract in a known manner the influence of the weight of the press platens on the surface pressure during the pressing operation, and to thus prevent a pressure increase from the uppermost to the lowermost story corresponding to the weight of the complete packet of press platens, but it is not possible to eliminate aperiodic variation in surface pressure between the stories above the press platens 7, between the platens 7 and 8 and below the platens 8, which is caused by the weight of the press platens 7 and 8. This variation in surface pressure, however, at maximum corresponds only to the weight of two press platens, and is thus in the majority of cases of no importance.

Instead of suspending the press platens 7 and 8 from the overlying press platen 6 and from the press platen 2 on the stationary press table respectively, as shown in FIG. 1, it is possible to support the press platens 7 and 8 from the underlying press platen 6 and from the press platen 5 on the movable press table, by means of suitable members positioned along the long sides of the press platens.

FIG. 3 illustrates an embodiment of such an arrangement, seen in vertical view from the side of the press and partly cut away. The FIG. 3 shows four press platens 2 or 6, 7, 8 and 6 or 5, arranged one below the other. The surface and wear plates, etc., secured to the press platens, have not been shown for the sake of simplicity. Secured to the press platen 7 is an abutment 21 and on the platen 8 is arranged a corresponding fitting 22 which supports a coil spring 23. Also secured on the platen 8 are two abutments 21, and two fittings 22 corresponding to said abutments 21 and supporting coil springs 23 are secured on the platen 6 or 5 positioned below said platen 8. The springs 23 are pre-compressed by bolts 24, the heads of which are designed as seatings for the upper ends of the springs 23 and the shafts of which are passed through holes in the attachments 22 and provided with nuts 25 and washers 26 on the bottom of the attachments. The abutments 21 on platens 7 and 8 rest on the heads of the bolts 24.

The pre-compressing force and spring characteristics of the springs 23 and the number of spring arrangements are chosen so that the total spring force of the springs 23 acting against the press platen 7 exceeds by a suitable value the weight of one press platen plus surface and wear plates, etc. and the material to be pressed placed thereon, and the platen 7 is therefore held supported from the platen 8 at a distance determined by the spring arrangements, provided that no downwardly directed forces other than weight act upon the same, but that the springs are compressed and the press opening between the platens 7 and 8 is closed when the press platen 7, after the press opening above the same has been fully closed, is subjected from above to a not too great force, suitably less than the weight of a press platen. The press platen 8 is thus also supported at a determined distance from the underlying press platen 6 or 5 until the press opening above the same has been fully closed, whereafter in turn it is closed by virtue of a press force exerted thereon from above.

A press provided with arrangements according to FIG. 3 for supporting the press platens 7 and 8 at a distance from the underlying press platen 6 or 5 instead of, as shown in FIGS. 1 and 2, by means for suspending the press platens 7 and 8 from the overlying press platens 6 or 2, will thus open and close the press openings principally in the same manner as the press according to FIGS. 1 and 2.. It is only the sequence in which the press openings are closed or opened which is changed.

One disadvantage associated with the array of resilient means is that press platens supported thus can yield downwardly momentarily at the start of movement of the press table 4, owing to the forces of inertia occurring in conjunction with the acceleration of said table. This disadvantage can be eliminated by supplementing the resilient supporting means with devices which fix the distance between the resiliently supported platen and the platen on which it is supported by means of a member which is removed when the press opening above the first mentioned platen has been closed through a distance corresponding to somewhat more than the path of acceleration of the press table 4. It is also possible, for instance, to use weighted levers instead of resilient means for supporting the press platens 7 and 8 at a distance from the underlying press platens 6 or 5. The weights on the levers are affected by the acceleration to a similar extent as the press platens themselves, and momentary closing movement of the press platens due to the forces of inertia are thereby automatically prevented.

The invention is naturally not restricted to the shown and described embodiments. Instead of lever mechanisms other known or novel arrangements may naturally be used to impart the movement of the press table 4 to the press platens 6. The number of press platens in each group may be 2, 3, 4 etc., depending on the desired ratio between the speed of the movable press table 4 and the relative speed between the two press platens in the individual stories. An embodiment having a different number of platens in one or more groupswhich may be desirable, for instance, when reconstructing old pressesis also conceivable within the scope of the invention. The means for suspending or supporting the remaining press platens in one group at a distance from the press platens 6 and 2 or 5 may also, naturally, comprise means other than those shown and described.

Compared with the previously known method of reducing the opening and closing speed of the individual stories relative to the speed of the mobile press table the invention affords the advantage that the arrangements for moving the press platens simultaneously with the press table are simplified to a very large extent. The presses are thereby made much more inexpensive and the simplified design also reduces the risk of interruptions in operation. The simplification in design also improves the possibilities of making the various arrangements sufficiently robust and reliable in operation.

The speed at which the press table moves cannot be as high as in the previously known method with respect to the closing and opening speed which can be permitted in the individual stories, but can, nevertheless, be selected as high as is generally possible with regard to the associated hydraulic equipment.

Neither will all the stories close approximately at the same time, as in the previously known method, but the stories will be closed approximately simultaneously in groups with a certain time difference between said groups. The maximum time difference between the closing moments, however, is only a fraction of that in a conventional press.

I claim:

1. Apparatus for closing and opening a multi-story press which comprises a stationary press table, a movable press table cooperatively connected to said stationary table, a plurality of first press platens mounted between said tables, one of said first platens being stationary and secured to said stationary table, means connecting the others of said first platens to said stationary table at spaced locations to move said other first platens toward or away from said stationary table to close or open the press at speeds approximately proportional to the respective distances of said other first platens from said stationary first platen when the press is fully open, a plurality of second press platens spaced between said tables with at least one of said second platens between each adjoining pair of said first platens, support means in- 7 dependent of said connecting means to connect each of said second platens to one of the respective adjoining first platens for movement to a position spaced between the respective adjoining platens in response to opening of the press without said support means oifering substantial resistance to reduction of the spacing between each said second platen and the respective adjoining platens in response to closing of the press.

2. An apparatus according to claim 1 wherein said support means comprises bolts connecting each of said second platens to the respective next higher platen.

3. An apparatus according to claim 1 wherein said support means comprises coil springs mounted between each of said second platens and the respective next lower 15 platen.

References Cited UNITED STATES PATENTS Tottle. Pasquali et al. Mains. Moore. Winegar. Carlson. Siempelkamp. Hutter. Schneider.

J. HOWARD FLINT, 111., Primary Examiner US. Cl. X.R. 

